1 files changed, 17 insertions, 2 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index b9526f749049..afc3ac5e57d7 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3689,6 +3689,20 @@ static int can_overcommit(struct btrfs_root *root,
         return 0;
 }
 
+static int writeback_inodes_sb_nr_if_idle_safe(struct super_block *sb,
+                                               unsigned long nr_pages,
+                                               enum wb_reason reason)
+{
+        if (!writeback_in_progress(sb->s_bdi) &&
+            down_read_trylock(&sb->s_umount)) {
+                writeback_inodes_sb_nr(sb, nr_pages, reason);
+                up_read(&sb->s_umount);
+                return 1;
+        }
+
+        return 0;
+}
+
 /*
  * shrink metadata reservation for delalloc
  */
@@ -3721,8 +3735,9 @@ static void shrink_delalloc(struct btrfs_root *root, u64 to_reclaim, u64 orig,
         while (delalloc_bytes && loops < 3) {
                 max_reclaim = min(delalloc_bytes, to_reclaim);
                 nr_pages = max_reclaim >> PAGE_CACHE_SHIFT;
-                writeback_inodes_sb_nr_if_idle(root->fs_info->sb, nr_pages,
-                                               WB_REASON_FS_FREE_SPACE);
+                writeback_inodes_sb_nr_if_idle_safe(root->fs_info->sb,
+                                                    nr_pages,
+                                                    WB_REASON_FS_FREE_SPACE);
 
                 /*
                  * We need to wait for the async pages to actually start before